A resource is a special variable, holding
a reference to an external resource. Resources
are created and used by special functions.
See the appendix
for a listing of all these
functions and the corresponding resource types.
The resource type was introduced in PHP 4
See also get_resource_type().
As resource types hold special handlers to opened
files, database connections, image canvas areas and
the like, you cannot convert any value to a resource.
Due to the reference-counting system introduced
with PHP 4's Zend Engine, it is automatically detected
when a resource is no longer referred to (just
like Java). When this is
the case, all resources that were in use for this
resource are made free by the garbage collector.
For this reason, it is rarely ever necessary to
free the memory manually by using some free_result
Persistent database links are special, they
are not destroyed by the
garbage collector. See also the section about persistent